diff --git a/climax/main/download_ERA5.py b/climax/main/download_ERA5.py
index b8885798221eb15f6be6a58a0c554a752cb5c77f..755303aff5b21268de47a6769b9bb6b9986cecd4 100644
--- a/climax/main/download_ERA5.py
+++ b/climax/main/download_ERA5.py
@@ -61,7 +61,7 @@ if __name__ == '__main__':
 
         # split the download to the different years: CDS API cannot handle
         # requests over the whole time period
-        Parallel(n_jobs=min(len(years, os.cpu_count())), verbose=51)(
+        Parallel(n_jobs=min(len(years), os.cpu_count()), verbose=51)(
             delayed(c.retrieve)(
                 product,
                 {**CONFIG, **{'variable': var, 'year': year}},